Fuel comprising a hydrazinoalkane and hydrazines



United States Patent Office 3,219,500 Patented Nov. 23, 1965 3,219,500 FUEL COMPRISING A HYDRAZINOALKANE AND HYDRAZINES Calvin E. Pannell, Lafayette, and Phyllis D. Oja, Walnut Creek, Calif., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed June 7, 1962, Ser. No. 202,346 6 Claims. (Cl. 149-36) This invention relates to propellant fuels and more particularly is concerned with an improved dense, liquid, nitrogen containing organic fuel for use in liquid bipropellant systems.

Anhydrous hydrazine is a desirable fuel for liquid propellant systems for rocket motors since it reacts spontaneously with certain oxidizers, e.g. nitric acid and concentrated hydrogen peroxide, thereby forming a noncarbonaceous propellant system. However, this fuel, which has a density of about 1.01 g./c-rn. also has an undesirably high freezing point of about 34 F. Therefore, to extend operable temperature range for using this fuel at lower temperatures it is ordinarily used as a mixture with uns-dimethyl hydrazine (UDMH) or monomethylhydrazine (MMH), for example, ordinarily at a 50-50 weight ratio. These mixtures have a freezing point reduced over that of hydrazine alone but also are less dense, e.g., UDMH has a density of about 0.79 g./cm. This decreased density of the mixed fuel is particularly undesirable since volume is of prime consideration in most rocket applications.

Now, unexpectedly the present invention provides a liquid propellant fuel composition having a density greater than anhydrous hydrazine, a desirably low freezing point and exhibiting substantially the same high specific impulse as shown by hydrazine itself.

This fuel composition of this invention comprises a hydrazinoalkane mixed with a member selected from the group consisting of hydrazine, mono and dimethyl substituted hydrazine and mixtures thereof. The term hydrazinoalkane as used herein refers to those compounds corresponding to the general formula designated hereinafter as EDH, is employed in the composition in admixture with hydrazine. With this two component fuel, the hereinbefore stated advantages are obtained, for example, utilizing a mixture containing from about 5 to about 95 weight percent EDH and from about 95 to about 5 weight percent substantially anhydrous hydrazine. Mixtures containing more than about 95 Weight percent EDH display a high viscosity which makes pumping of the mixture somewhat diflicult. Desirably the fuel composition will contain from about 20 to about 80 weight percent EDH, balance hydrazine and preferably a 50-50 weight percent composition is used.

The addition of the hydrazinoalkane to hydrazine- UMDH or other hydrazine containing liquid propellant fuel mixtures also provides both depressed freezing of the liquid and increased density advantage to such mixtures. To illustrate, a ternary mixture of from about 10 to weight percent UMDH, about 40 to weight percent hydrazine and about 5 to 50 Weight percent EDH provide a satisfactory liquid propellant. Preferably, this ternary composition will contain about equal parts by weight of the three components.

The hydrazinoalkanes are prepared by the method described in copending application, Serial No. 202,347, filed even date herewith. This reaction comprises reacting the corresponding halogenated alkane with aqueous hydrazine at a hydrazine hydrate/halogenated alkane molar ratio of from about 10 to 25. This reaction is carried out at ambient pressures over a temperature range of from about 560 C., preferably 3540 C., employing the hydrazine as an aqueous solution containing from about 40 to about 80 weight percent hydrazine. The reaction readily is accomplished in a reactor vessel equipped with a stirring mechanism using intermittent agitation of the reactants during the reaction period. Completion of the reaction is observed by the disappearance of the two phases and formation of a substantially homogeneous reaction mass, the aqueous hydrazine and halogenated hydrocarbon initially being substantially immiscible.

The excess aqueous hydrazine is removed, eg by distillation, from the product mass, and the hydrazinoalkane product subsequently converted into the acid salt. This salt can be regenerated as the free base, and a purified product recovered by distillation.

The propellant fuel composition of the present invention can be employed in a liquid propellant system in the same manner and with the same oxidants as are used for hydrazine alone.

The following examples will serve to illustrate further the present invention, but are not meant to limit it thereto.

Example 1 The freezing point for a number of EDH-anhydrous hydrazine binary mixtures was determined employing standard freezing point determination techniques. The results of these tests are presented in Table I.

TABLE L-FREEZING POINTS OF 1,2-DIHYDRAZINOEIH- ANE ANH. HYDRAZINE MIXTURES Run No. EDH, Wt. Hydrazine, F.P., C.

percent wt. percent In a second series of tests the density at room temperature, about 25 C., of a number of EDH-anhydrous hydrazine mixtures was determined. Table II shows the results of these measurements:

TABLE IL-DENSITIES OF 1,2-DIHYDRAZINOETHANE- ANH. HYDRAZINE MIXTURES EDH, wt. Hydrazine, Density, Run N0 percent wt. percent g., cm.

The viscosity of a number of EDH-anhydrous hydrazine mixtures was determined using a Gardner-Holdt viscome- 3 ter tube. The measurements were taken at 25 C. The results of these studies are presented in Table III.

TABLE IIL-VISCOSI'IIES OF 1,2-DIHYDRAZINOETHANE- ANH. HYDRAZINE MIXTURES Example 2 A liquid propellant system was prepared employing about 61.7 weight percent of N and 38.3 weight percent of a 50-50 mixture of EDH and hydrazine. The fuel and oxidizer components were fed from separate storage reservoirs into a combustion zone, whereupon contact they spontaneously ignited and readily burned. The calculated specific impulse of the reaction mixture was 290.1 seconds which is substantially the same as exhibited by a N O -hydrazine system itself.

In a manner similar to that described for the foregoing example, a 50-50 weight percent mixture of EDH and UDMH can be employed as a fuel in a bipropellant system with hydrogen peroxide oxidizer. Likewise a ternary mixture of about equal parts by weight of EDH-UDMH- N I-L; can be used as a fuel with a fuming nitric acid oxidant. Again a mixture of 20 weight percent 1,2,3,4- tetrahydrazinobutane and 80 weight percent hydrazine can be employed as a liquid fuel in a bi-propellant system employing liquid oxygen as an oxidizer. Also 1,2,3,4,5,6- hexahydrazinohexane can be admixed with hydrazine to provide a propellant fuel having the desired characteristics set forth herein.

Various modifications can be made in the present invention without deparating from the spirit or scope thereof, for it is to be understood that we limit ourselves only as defined in the appended claims.

We claim:

1. A liquid propellant fuel comprising in combination a hydrazinoalklane and a member selected from the group consisting of hydrazine, mono and dimethyl substituted hydrazines and mixtures thereof, said hydrazinoalkane being a compound corresponding to the general formula LHI INHQJn wherein n is an integer ranging from 2 to about 6, the amount of said hydrazinoalkane in said composition ranging from about 5 percent, based on the total composition weight, up to an amount wherein said composition becomes too viscous for ready handling.

2. In a liquid propellant composition consisting essentially of hydrazine, mono and dimethyl hydrazines and mixtures thereof, the improvement which comprises incorporating into said composition at least 5 weight percent of a hydrazinoalkane freezing point depressant and density increaser corresponding to the general formula Elli l LHI INH 2 n wherein n is an integer ranging from 2 to about 6.

3. A liquid propellant composition comprising from about 5 to about 95 weight percent 1,2-dihydrazinoethane and from about 95 to about 5 percent substantialy anhydrous hydrazine.

4. A liquid propellant composition comprising about weight percent 1,2-dihydrazinoethane and about 50 weight percent substantialy anhydrous hydrazine.

5. A liquid rocket propellant comprising from about 10 to about 40 weight percent uns.-dimethylhydrazine, about 40 to about weight percent hydrazine and about 5 to 50 weight percent 1,2-dihydrazinoethane.

6. A liquid propellant fuel which comprises in about equal weight proportions a ternary mixture of uns.-dimethylhydrazine, hydrazine and 1,2-dihydrazinoethane.

References Cited by the Examiner UNITED STATES PATENTS 2,822,354 2/1958 Uranck et al 260-583 X REUBEN EPSTEIN, Primary Examiner.

CARL D. QUARFORTH, LEON D. ROSDOL,

Examiners. 

1. A LIQUID PROPELLANT FUEL COMPRISING IN COMBINATION A HYDRAZINOALKLANE AND A MEMBER SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE, MONO AND DIMETHYL SUBSTITUTED HYDRAZINES AND MIXTURES THEREOF, SAID HYDRAZINOALKANE BEING A COMPOUND CORRESPONDING TO THE GENERAL FORMULA 